1. Field of the Invention
The present invention relates to a method and an apparatus for controlling reproduction of image data.
2. Related Background of the Art
In recent years, development of a multimedia technology which synthetically deals with a plurality of media for audio data, image data, etc. has been proceeding. A method and apparatus capable of efficiently processing the data of the respective media have been demanded.
In particular, the image data is greater in terms of quantity than the audio data and, therefore, requires efficient processing.
A dynamic image data reproducing device generally for a domestic use may embrace, e.g., a magnetic tape reproducer, a magnetic disk reproducer, an optical disk reproducer, etc..
In the magnetic tape reproducer, an induced voltage generated between a magnetic substance on the tape surface and a magnetic head is amplified and shaped. The voltage is thereby converted into digital signals. The digital signals are further converted into analog signals. The analog signals are output from an image output unit as well as from an audio output unit.
More specifically, according to the magnetic tape reproducer, an array {N, N, S, N, S, S, N, S, N, . . . } of the magnetic substance is discriminated based on a waveform of the induced voltage. This array is converted into an array {1, 1, 0, 1, 0, 0, 1, 0, 1, . . . } of digital signals. Further, the magnetic tape reproducer is constructed to convert the digital signals into analog signals and output the analog signals from an image output unit such as a CRT (cathode ray tube), etc. and an audio output unit such as a loudspeaker, etc. This magnetic tape reproducer exhibits such a characteristic that the data is sequentially read in accordance with rotations of a reel for feeding and winding the magnetic tape.
The magnetic disk reproducer also reads the image data and the audio data on the basis of the array of the magnetic substance on the disk surface as in the magnetic tape reproducer. This magnetic disk reproducer is capable of reading the data recorded on the magnetic disk at random. That is, the magnetic head of the magnetic disk reproducer is movable between an outer edge and a central portion of the rotating disk. The magnetic head is therefore capable of immediately reading the data stored in an arbitrary location on the disk.
The optical disk reproducer is a device in which laser technology is introduced into the principle of the magnetic disk.
Namely, on the optical disk, the digital signals are recorded on a rugged portion on the disk surface which is termed a pit. In the optical disk reproducer, the disk surface is irradiated with a laser beam from the optical head. The signals are read on the assumption that a pit array is conceived as an array of the digital signals. Then, the optical disk reproducer converts the digital signals read from the optical disk into analog signals. The analog signals are outputted from the image output unit and the audio output unit. This optical disk reproducer is capable of reading the data at random as in the case of the magnetic disk reproducer described herein above.
Moreover, the optical disk reproducer has a characteristic in which the data can be read with no contact between the head for reading out the data and the disk. For this reason, a degradation both in the head and in the disk can be prevented in contrast with the magnetic tape reproducer where the head contacts the recording medium.
The magnetic tape reproducer has a higher spread rate among the image reproducing devices and is enough of software of the magnetic tape. The-software of the magnetic tape includes, e.g., video software recorded with movie information, instructional video software in which the professionals in a variety of fields show their skills, enterprise introduction video software for recruiting the staff or improving images of enterprises, and video magazine software for introducing the items to be appeared on magazines in the form of dynamic images.
On the other hand, high-quality sounds and pictures can be recorded on the optical video disk, and hence software is recorded with images and sounds in a live musical performance.
Next, the operational principle of the dynamic image data reproducing device will be briefly explained.
The dynamic image data reproducing device reads the dynamic image data stored on the recording medium such as a magnetic tape, a magnetic disk or an optical disk according to a frame unit. Subsequently, the dynamic image data reproducing device outputs the frame data read out from the recording medium in the form of the image data and the audio data through a display unit and an output unit such as a loudspeaker.
Further, a method of recording each item of frame data while compressing the data is given as a method of recording the dynamic image data. When using this method, the dynamic image data reproducing device performs an extension process based on a compression process algorithm with respect to the dynamic image data. The dynamic image data reproducing device thereafter outputs the image data and the audio data. According to this method, recording areas on the recording medium are usable at a high efficiency.
Here exist multiple types of dynamic image data reproducing devices. Performances of a processor and a memory employed for the dynamic image data reproducing device differ depending on the type thereof. This is conductive to a problem that a regenerative processing time of the dynamic image data reproducing device becomes different depending on the type thereof.
Especially, the optical disk reproducer and the magnetic disk reproducer read the data at random, and, therefore, a rate of dependency on the performances of the processor and of the memory is large.
For example, if the same dynamic image data is reproduced by different types of dynamic image data reproducing devices, the reproducing time may be different. Further, the reproductive process corresponding to a recording time (i.e., the reproductive process in the same reproducing time as the recording time) is inexecutable in some cases.